Watch-glass



J. H. PURDY. Watch-Glass.

No. 221,923. I Patented May. 25, I880.

UNITED STATES PATENT OFFICE.

JOHN H. PURDY, OF CHICAGO, ILLINOIS.

WATCH- GLASS.

SPEGIFICATION forming part of Letters Patent No. 227,923, dated May 25, 1880.

Application filed February 20, 1880.

To all whom it may concern:

Be it known that I, JOHN H. PURDY, of Chicago, in the State of Illinois, have invented a new and useful Improvement in Watch- Glasses, of which the following is a specification.

My invention consists in substituting for the glass usually employed in watch-cases to protect the dial and hands one having a central cavity to receive the most projecting portion of the movement.

The object of my invention is to produce a glass that, while having the strongest form, will not increase the thickness of the watch it is used on to an undesirable amount.

The invention is designed to be used on watches of the kind known as open-faced, having the central stem of the movement projecting above the hands to receive a key when it is desired to change the position of the hands; and it consists in using a glass having beveled edges and flat parallel surfaces with a hollow or cavity formed in its under side that is, the side having the largest surface to admit the central stem of the movement.

In the accompanying drawings, Figure l is a view of the upper side of my glass; Fig. 2, a section, and Fig. 3 a view of the underside of the same.

H is the watch-glass, having parallel sides I) c. The side 0 is designed to be placed neXt to the watch-dial, and has a recess, (1, in its center, that I make as small 'and of such form as can be conveniently made, large and deep enough to admit the part desired, but not entirely through the glass.

A glass made of the form described will, when placed on a watch, diminish the whole thickness of the watch by the amount the central stem projects above the hour-hand and be quite as strong as if the glass had no recess.

I am aware that watch-glasses have heretofore been made having a flat upper surface and a concave under side to accomplish a part of my object; but the glass being made thinner is not as strong as a flat glass having edges, sides, and center made in the form I have described.

I claim as my invention- A watch-glass having flat parallel surfaces and beveled edges and a cavity in the center of the largest surface, substantially as and for the purpose described.

JOHN H. 'PURDY.

Witnesses:

Tnos. B. JEFFERY, FELIX J. GRIFFEN. 

